The present invention generally relates to the field of telecommunications, and more particularly, to the field of shared voice and data communications on existing electrical two-wire pairs.
Data communication via the public switched telephone network (PSTN) is ever increasing. As known to those skilled in the art, the PSTN is comprised of local and/or central offices which provide telephone service to end users. Typically, the end user is connected to the central office by a two-wire pair which is also called a local loop. More and more, these two-wire pairs arc employed for data communication using digital subscriber loop (DSL) technology to facilitate high speed data communication.
Due to the demand for both voice and data communication using existing two-wire pairs, telephone service providers presently achieve concurrent telephone operation and high speed data operation using digital subscriber loop (DSL) technologies. In particular, plain old telephone service (POTS) uses a bandwidth of approximately 100-4000 Hertz to communicate voice signals. Data communication using DSL technologies typically operates at a bandwidth with a lower cutoff frequency of approximately 30 Kilohertz and an upper cutoff frequency that varies significantly depending on the specific type of DSL technology employed. Concurrent voice and data communication is established on the same local loop as the bandwidths do not overlap.
As is known in the art, however, when DSL and voice POTS communications share a two-wire pair, POTS-splitters are required at the customer premises. As is further known, POTS-splitters electronically filter the low frequency POTS signals from reaching DSL communication devices, and the relatively high frequency DSL signals from reaching the POTS devices such as telephones, facsimile machines, modems, etc. Unfortunately, the installation of POTS-splitters imposes a relatively significant and undesired cost burden on the customer.
To explain further, a POTS-splitter includes a low pass filter that rejects signals at frequencies higher than the 100-4000 Hertz frequency bandwidth. Also, most DSL technologies include a front-end high pass filter that rejects any frequencies below the 30 Kilohertz cutoff. POTS-splitters may be installed at the customer premises at the point of entry of the local loop into the customer premises or at each POTS device. Either manner of installation may present significant cost to the consumer.
Another additional cost imposed with the use of POTS-splitters is cost of installation of POTS-splitters at the central office side of the local loop. This cost creates an additional barrier to the use of high speed data communication devices such as DSL or other technology.
In addition, POTS-splitters also cause problems for data communication using technology other than DSL. Specifically, with these technologies, the local loop cannot be used for communication below 30 Kilohertz when POTS-splitters are employed even though POTS service is not being used. This reduces the potential data rates by as much as 256 Kbps.
Accordingly, there is a need to provide a system that allows shared (e.g., voice and high speed data) usage of a two-wire pair, without the expense associated with DSL services. In addition, there is also a need for technology which will allow data communication using the full bandwidth available when POTS is inactive on the local loop, thereby maximizing the rate of data communication.
According to a first embodiment of the present invention, a local loop interceder is installed in a central office onto the local loop that will allow the local loop to be used for voice or data communication. The local loop interceder features a switching mechanism having a first position and a second position which define both a first and a second signal pathway. The first signal pathway is capable of electrically coupling the local loop to a switched telephone network at the central office, thereby facilitating electrical communication between the local loop and the public switched telephone network (PSTN). The second signal pathway is capable of electrically coupling the local loop to a high speed data communication device, thereby facilitating electrical communication between the local loop and the high speed data communication device which acts as an interface for high speed data communication networks. The local loop interceder of the first embodiment also includes sensing circuitry to various signal activity and other system conditions to control the interceder functions.
According to a second embodiment, there is provided a local loop interceder which, in addition to the features of the first embodiment, includes a third signal pathway which facilitates transmission from the high speed data communication device to the PSTN, thereby facilitating the communication of a voice signal between the high speed data communication device and the PSTN. According to the second embodiment, the high speed data communication device facilitates the communication of simultaneous voice and data (SVD). Consequently, the local loop interceder according to the second embodiment provides a first signal pathway from the local loop to the PSTN for regular telephone service on the local loop. Also provided is a second signal pathway to facilitate the transmission of a data signal or an SVD signal from the local loop to an SVD modem. Finally, the third signal pathway is provided between the SVD modem to the PSTN to be used to transmit a voice signal demodulated from a simultaneous voice and data signal received from the local loop to the PSTN.
Additionally, it should be noted that the present invention does not require telephone company installation of equipment at the customer premises, thereby reducing the cost barrier that prohibits the use of DSL and other high speed data communication technology by the average end user.
The present invention can also be conceptualized as providing a method for electrically coupling a switched telephone network, a data communication device, and a local loop to facilitate voice and data communications. In this regard, the method can be broadly summerized by the following steps: providing a first and second signal pathways to couple respectively the local loop to the switched telephone network and the local loop to the data communication device; sensing signal activity on said first and second signal pathways; and coupling the local loop to the data communication device or the local loop to the switched telephone network based upon the sensed signal acitivity.
Other features and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional features and advantages be included herein within the scope of the present invention, as defined by the claims.